The present invention relates to a flat panel display and, more particularly, to a field emission type flat panel display.
In recent years, as a flat panel display such as an FED (Field Emission Display) or a flat vacuum fluorescent display in which electrons emitted from an electron-emitting source serving as a cathode bombard a light-emitting portion formed of phosphors on a counterelectrode to emit light, various types that use nanotube fibers, e.g., carbon nanotubes or carbon nanofibers, as the electron-emitting source have been proposed (for example, see Japanese Patent Laid-Open Nos. 2002-343281 and 2004-193038). FIG. 9 is a partially exploded view showing an example of a conventional flat panel display which uses nanotube fibers as electron-emitting sources.
This flat panel display has a cathode substrate 100 having a substrate 101 made of glass or the like, an anode substrate 200 having an at least partially transmitting front glass 201, and a gate substrate 300 which is disposed substantially parallel to the substrate 101 and front glass 201. The substrate 101 of the cathode substrate 100 and the front glass 201 of the anode substrate 200 are arranged to oppose each other through a frame-like spacer glass (not shown) and are adhered to the spacer glass with low-melting frit glass to form an envelope. The interior of the envelope is maintained at a vacuum degree on the order of 10−5 Pa.
The cathode substrate 100 has the substrate 101 and a plurality of substrate ribs 102 which vertically extend on that surface of the substrate 101 which opposes the gate substrate 300 at a predetermined interval to be parallel to each other. Cathode electrodes 103 which substantially form matrices when seen from the top and which are obtained by fixing electron-emitting sources made of nanotube fibers such as carbon nanotubes or carbon nanofibers to the surfaces of metal members such as 42-6 alloy members are disposed on those regions of the substrate 101 which are sandwiched by the substrate ribs 102.
The anode substrate 200 has the front glass 201, a plurality of black matrices 202 which have rectangular sections and are formed on that surface of the front glass 201 which opposes the gate substrate 300 at a predetermined interval to form stripes in a direction parallel to the substrate ribs 102, red-, green- and blue-emitting phosphor films 203R, 203G, and 203B which are formed on those regions of the front glass 201 which are sandwiched by the black matrices 202, metal-backed films 204 which are formed on regions sandwiched by the phosphor films 203R, 203G, and 203B to serve as anodes, and a plurality of front ribs 205 which are formed on the black matrices 202 and have rectangular sections.
The gate substrate 300 disposed in the envelope comprises a glass plate 301, a flat electrode 302 which is formed on the surface of the glass plate 301 on the anode substrate 200 side, band-like gate electrodes 303 formed on the surface of the glass plate 301 on the cathode substrate 100 side to correspond to the phosphor films 203R, 203G, and 203B, and an insulating layer 304 which is formed on the gate electrodes 303. The gate substrate 300 has electron-passing holes 305, substantially circular when seen from the top, which are formed at regions where the band-like gate electrodes 303 and matrix-like cathode electrodes 103 overlap, to extend through the flat electrode 302, glass plate 301, gate electrodes 303, and insulating layer 304. Each electron-passing hole 305 forms a pixel of the flat panel display. The gate substrate 300 is sandwiched by the substrate ribs 102 of the cathode substrate 100 and the front ribs 205 of the anode substrate 200.
In this flat panel display, when a predetermined potential difference is applied between the gate substrate 300 and cathode electrodes 103 such that the gate substrate 300 side has a positive potential, electrons extracted from those regions of the cathode electrodes 103 which intersect the gate electrodes 303 are emitted from the electron-passing holes 305.
More specifically, first, a voltage is applied to the flat electrode 302 to set it to have a higher potential than that of the cathode electrodes 103, and an electric field is applied to the surfaces of the cathode electrodes 103 in advance. When a voltage is further applied to the gate electrodes 303 to set them to have a higher potential than that of the cathode electrodes 103, an electric field is applied to the cathode electrodes 103 from the outer surfaces of the gate electrodes 303 which form the electron-passing holes 305, to extract electrons from electron-emitting sources 111 disposed on the surfaces of the cathode electrodes 103. The electrons are accelerated by the flat electrode 302 to which a voltage has been applied to set it to have a positive potential with respect to the gate electrodes 303, and emitted from the electron-passing holes 305 to the front glass 201 side.
If a potential (accelerating voltage) higher than that of the flat electrode 302 is applied to the metal-backed films 204, the electrons emitted from the electron-passing holes 305 are accelerated toward the metal-backed films 204, and penetrate through the metal-backed films 204 to bombard the phosphor films 203G, 203B, and 203R. Thus, the phosphor films emit light.
A method of manufacturing such a flat panel display will be described.
The cathode substrate 100 is formed in the following manner. First, an insulating paste such as a vitreous paste is printed on the substrate 101 with a known printing method such as screen printing to form the substrate ribs 102 on one surface of the substrate 101. Subsequently, the cathode electrodes 103 with electron-emitting surfaces disposed on their surfaces are disposed on those regions of the substrate 101 which are sandwiched by the substrate ribs 102. This forms the cathode substrate 100. The cathode electrodes 103 described above can be formed by disposing the electron-emitting sources on their surfaces by CVD or the like.
The anode substrate 200 is formed in the following manner. First, the front glass 201 is prepared. An insulating paste such as a vitreous paste is printed on the front glass 201 with a known printing method such as screen printing to form the black matrices 202 on one surface of the front glass 201. Subsequently, the phosphor materials of the phosphor films 203R, 203G, and 203B are printed on the front glass with a known printing method such as screen printing to form the red-, green-, and blue-emitting phosphor films 203R, 203G, and 203G on those regions on the front glass 201 which are sandwiched by the black matrices 202. Then, the metal-backed films 204 are formed on the phosphor films 203R, 203G, and 203B with a known deposition method. Finally, a glass paste is repeatedly printed on the black matrices 202 with a known printing method such as screen printing to form the front ribs 205. Alternatively, the front ribs 205 may be formed by fixing members made of glass or a ceramic material formed into predetermined shapes to the black matrices 202 by adhesion using a frit paste, or by contact bonding using metal films.
The gate substrate 300 is formed in the following manner. First, the glass plate 301 is prepared, and the flat electrode 302 is formed on its one surface by printing or sputtering. Subsequently, the band-like gate electrodes 303 are formed on the other surface of the glass plate 301 by printing or sputtering. The insulating layer 304 is then formed on the other surface of the glass plate 301 by printing or photolithography to cover the gate electrodes 303. Finally, the electron-passing holes 305 are formed by sandblasting to extend through the flat electrode 302, glass plate 301, gate electrodes 303, and insulating layer 304.
When the cathode substrate 100, anode substrate 200, and gate substrate 300 formed in the above manner are assembled, a flat panel display is formed. More specifically, first, the gate substrate 300 is sandwiched with the substrate ribs 102 of the cathode substrate 100 and the front ribs 205 of the anode substrate 200. In this state, the rim of the substrate 101 of the cathode substrate 100 and the rim of the front glass 201 of the anode substrate 200 are adhered to frame-like spacer glass with low-melting frit glass to form an envelope. The interior of the envelope is vacuum-evacuated to form the flat panel display. In this flat panel display, the gate substrate 300 is fixed and held by the anode substrate 200 and gate substrate 300 by pressurization with an atmospheric pressure.
In the flat panel display as described above, in order to improve the luminance uniformity, it is important that the distance between the cathode electrodes 103 of the cathode substrate 100 and the gate electrodes 303 of the gate substrate 300 is uniform at any location. In order to realize driving at a low voltage, it is necessary to decrease the distance between the cathode electrodes 103 and gate electrodes 303. For these purposes, conventionally, as described above, the insulating layer 304 is formed by printing or photolithography, or a thin glass plate which is formed thin to have a uniform thickness in advance is used as the insulating layer 304, so the distance between the cathode electrodes 103 and gate electrodes 303 becomes uniform and short.
When printing or photolithography as described above is employed, it is difficult to form a uniformly thin, crack-free layer as the insulating layer 304. It is also difficult to form the insulating layer 304 so as not to attach to the side walls of the electron-passing holes 305 or the like. When using a thin glass plate as the insulating layer 304, if the glass plate is excessively thin, it tends to break, and accordingly the thickness and size of the glass plate are limited. Therefore, in the conventional flat panel display, it is difficult to uniform and decrease the distance between the cathode electrodes and gate electrodes.